Remove calls to currentThread() in _Condition methods that were side-effect.

Side-effects were deemed unnecessary and were causing problems at shutdown
time when threads were catching exceptions at start time and then triggering
exceptions trying to call currentThread() after gc'ed.  Masked the initial
exception which was deemed bad.

Fixes bug #754449 .

Lib/threading.py

@@ -193,7 +193,6 @@ class _Condition(_Verbose):
             return True
 
     def wait(self, timeout=None):
-        currentThread() # for side-effect
         assert self._is_owned(), "wait() of un-acquire()d lock"
         waiter = _allocate_lock()
         waiter.acquire()
@@ -235,7 +234,6 @@ class _Condition(_Verbose):
             self._acquire_restore(saved_state)
 
     def notify(self, n=1):
-        currentThread() # for side-effect
         assert self._is_owned(), "notify() of un-acquire()d lock"
         __waiters = self.__waiters
         waiters = __waiters[:n]